Leadless intra-cardiac medical device with built-in telemetry system

ABSTRACT

A leadless intra-cardiac medical device is configured to be implanted entirely within a heart of a patient. The device includes an intra-cardiac extension and a housing. The intra-cardiac extension includes a loop body having at least one loop segment retaining at least one coil group that is configured to one or both of receive and transmit radio frequency (RF) energy, wherein the loop body is configured to extend into a first chamber of the heart. The housing is in electrical communication within the loop body, and includes a transceiver, control logic and an energy source. The housing is configured to be securely attached to an interior wall portion of a second chamber of the heart, wherein the transceiver is configured to communicate with an external device through the RF energy.

CROSS REFERENCE TO RELATED APPLICATIONS

This application relates to and claims priority benefits from U.S.Provisional Application No. 61/555,943, filed Nov. 4, 2011, entitled“Intra-Cardiac Medical Device with Built-In Telemetry System,” which ishereby incorporated by reference in its entirety. This application alsorelates to U.S. patent application Ser. No. 13/352,101, filed Jan. 17,2012, entitled “Single-Chamber Leadless Intra-Cardiac Medical Devicewith Dual Chamber Functionality and Shaped Stabilization Intra-CardiacExtension”, now U.S. Pat. No. 8,700,181, which is hereby incorporated byreference in its entirety.

FIELD OF THE INVENTION

Embodiments of the present invention generally relate to implantablemedical devices, and more particularly to leadless intra-cardiac medicaldevices having a built-in telemetry system. As used herein, the term“leadless” generally refers to an absence of electrically-conductiveleads that traverse vessels outside of the intra-cardiac space, while“intra-cardiac” means generally, entirely within the heart andassociated vessels, such as the SVC, IVC, CS, pulmonary arteries and thelike.

BACKGROUND OF THE INVENTION

Current implantable medical devices for cardiac applications, such aspacemakers, include a “housing” or “can” and one or moreelectrically-conductive leads that connect to the can through anelectro-mechanical connection. The can is implanted outside of theheart, in the pectoral region of a patient and contains electronics(e.g., a power source, microprocessor, capacitors, etc.) that providepacemaker functionality. The leads traverse blood vessels between thecan and heart chambers in order to position one or more electrodescarried by the leads within the heart, thereby allowing the deviceelectronics to electrically excite or pace cardiac tissue and measure orsense myocardial electrical activity.

To sense atrial cardiac signals and to provide right atrial chamberstimulation therapy, the can is coupled to an implantable right atriallead including at least one atrial tip electrode that typically isimplanted in the patient's right atrial appendage. The right atrial leadmay also include an atrial ring electrode to allow bipolar stimulationor sensing in combination with the atrial tip electrode.

Before implantation of the can into a subcutaneous pocket of thepatient, however, an external pacing and measuring device known as apacing system analyzer (PSA) is used to ensure adequate lead placement,maintain basic cardiac functions, and evaluate pacing parameters for aninitial programming of the device. In other words, a PSA is a systemanalyzer that is used to test an implantable device, such as animplantable pacemaker.

To sense the left atrial and left ventricular cardiac signals and toprovide left-chamber stimulation therapy, the can is coupled to the“coronary sinus” lead designed for placement in the “coronary sinusregion” via the coronary sinus ostium in order to place a distalelectrode adjacent to the left ventricle and additional electrode(s)adjacent to the left atrium. As used herein, the phrase “coronary sinusregion” refers to the venous vasculature of the left ventricle,including any portion of the coronary sinus, great cardiac vein, leftmarginal vein, left posterior ventricular vein, middle cardiac vein,and/or small cardiac vein or any other cardiac vein accessible by thecoronary sinus.

Accordingly, the coronary sinus lead is designed to: receive atrialand/or ventricular cardiac signals; deliver left ventricular pacingtherapy using at least one left ventricular tip electrode for unipolarconfigurations or in combination with left ventricular ring electrodefor bipolar configurations; deliver left atrial pacing therapy using atleast one left atrial ring electrode as well as shocking therapy usingat least one left atrial coil electrode.

To sense right atrial and right ventricular cardiac signals and toprovide right-chamber stimulation therapy, the can is coupled to animplantable right ventricular lead including a right ventricular (RV)tip electrode, a right ventricular ring electrode, a right ventricularcoil electrode, a superior vena cava (SVC) coil electrode, and so on.Typically, the right ventricular lead is inserted transvenously into theheart so as to place the right ventricular tip electrode in the rightventricular apex such that the RV coil electrode is positioned in theright ventricle and the SVC coil electrode will be positioned in theright atrium and/or superior vena cava. Accordingly, the rightventricular lead is capable of receiving cardiac signals, and deliveringstimulation in the form of pacing and shock therapy to the rightventricle.

Although a portion of the leads are located within the heart, asubstantial portion of the leads, as well as the can itself are outsideof the patient's heart. Consequently, bacteria and the like may beintroduced into the patient's heart through the leads, as well as thecan, thereby increasing the risk of infection within the heart.Additionally, because the can is outside of the heart, the patient maybe susceptible to Twiddler's syndrome, which is a condition caused bythe shape and weight of the can itself. Twiddler's syndrome is typicallycharacterized by a subconscious, inadvertent, or deliberate rotation ofthe can within the subcutaneous pocket formed in the patient. In oneexample, a lead may retract and begin to wrap around the can. Also,leads may dislodge from the endocardium and cause the device tomalfunction. Further, in another typical symptom of Twiddler's syndrome,the device may stimulate the diaphragm, vagus, or phrenic nerve,pectoral muscles, or brachial plexus. Overall, Twiddler's syndrome mayresult in sudden cardiac arrest due to conduction disturbances relatedto the device.

In addition to the foregoing complications, implanted leads mayexperience certain further complications, such as incidences of venousstenosis or thrombosis, device-related endocarditis, lead perforation ofthe tricuspid valve and concomitant tricuspid stenosis; and lacerationsof the right atrium, superior vena cava, and innominate vein orpulmonary embolization of electrode fragments during lead extraction.

To combat the foregoing limitations and complications, small sizeddevices configured for intra-cardiac implant have been proposed. Thesedevices, termed leadless pacemakers (LLPM) are typically characterizedby the following features: they are devoid of leads that pass out of theheart to another component, such as a pacemaker can outside of theheart; they include electrodes that are affixed directly to the can ofthe device; the entire device is attached to the heart; and the deviceis capable of pacing and sensing in the chamber of the heart where it isimplanted.

It can be appreciated, however, that a leadless pacing system needs tobe compact enough to fit within the heart. At the same time, the pacingsystem requires a power source to operate. Accordingly, the pacer moduleincludes a battery contained therein. Typically, the pacer module has ahousing having a battery that may take up as much as 75% of the internalvolume of the housing. Therefore, the pacer module itself may be bulkyand occupy a relatively large volume within the heart chamber, which mayadversely impact proper heart function.

Moreover, many pacing systems include telemetric subsystems thatcommunicate with a remote programmer or patient care system. Telemetricsubsystems include an antenna that communicates with the remote patientcare system through radio frequency (RF) signals. Conventional antennaare relatively large, too large to fit into the housing of a leadlesspacemaker.

SUMMARY OF THE INVENTION

Certain embodiments provide a leadless intra-cardiac medical device(LIMD) configured to be implanted entirely within a heart of a patient.The device includes an intra-cardiac (IC) extension and a housing. Theintra-cardiac extension may include a loop body having at least one loopsegment retaining at least one coil group that is configured to receiveand/or transmit radio frequency (RF) energy. The loop body may beconfigured to extend into a first chamber of the heart.

The housing is in electrical communication within the loop body and isconfigured to be securely attached to an interior wall portion of asecond chamber of the heart. The housing includes a transceiver that isconfigured to communicate with an external device through the RF energy.

The housing further includes an energy source that may be configured tobe recharged through current induced within the at least one coil group.The current may be induced by a magnetic field caused by the RF energy.The loop segment may include at least one electrode secured thereto. Theloop segment may be configured to contact a portion of an internal wallof the heart. The housing may be configured to provide one or both ofsensing or stimulus through the at least one electrode.

The loop segment may include a plurality of interconnected loopsegments. Each of the plurality of interconnected loop segments may becommonly aligned and oriented with respect to one another and areference plane. Alternatively, the plurality of interconnected loopsegments may include a first group of loop segments and a second groupof loop segments. The first group of loop segments may be oriented withrespect to first and second orthogonal axes and the second group of loopsegments may be oriented with respect to first and third orthogonalaxes. A first of the plurality of interconnected loop segments may bealigned in a first orientation and a second of the plurality ofinterconnected loop segments may be aligned in a second orientation. Thefirst orientation differs from the second orientation so that the firstand second of the plurality of interconnected loop segments are out ofplane with one another.

The loop segments may be formed with a perimeter that flares in adirection generally toward and away from a lateral axis with respect toa longitudinal axis of the loop body. The loop segments may include aperimeter shaped as a disc, oval, circle, tube, rectangle, or triangle.

The IMD system may also include a protective tube between the loop bodyand the housing. The loop segments may be proximally or distally locatedfrom the housing.

Certain embodiments provide a method of operating a leadlessintra-cardiac medical device (LIMD) within a heart of a patient. Thedevice may include a loop body having at least one loop segmentretaining at least one coil group within a first internal portion of theheart, and a housing connected to the loop body and secured within asecond internal portion of the heart. The method may include emittingradio frequency (RF) energy from an external device to the IMD,generating an induced current in the loop body through the RF energy,passing the induced current from the loop body within the first internalportion of the heart to the housing secured within the second internalportion of the heart, and communicating between the IMD and the externaldevice through the generating and passing.

The method may also include recharging a rechargeable energy source ofthe LIMD through the induced current.

The method may also include contacting an internal wall of the firstinternal portion of the heart with at least one electrode on a portionof the loop body. The at least one housing may be configured to provideone or both of sensing or stimulus through the at least one electrode.

The method may also include calibrating the LIMD after implantation intothe heart of the patient. The calibrating may include adjusting drivefrequencies of the at least one loop segment. The method may alsoinclude tuning the loop segments through the adjusting.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a leadless intra-cardiac medical device (LIMD)implanted within a heart of a patient that includes housing and anintra-cardiac extension.

FIG. 2 illustrates an introducer assembly introducing an LIMD into aheart of a patient.

FIG. 3 illustrates an introducer assembly disengaging from an LIMDwithin a heart of a patient.

FIG. 4A illustrates an LIMD.

FIG. 4B illustrates an isometric view of adjacent loop segments of aloop body of an intra-cardiac extension.

FIG. 5 illustrate a block diagram of electronics associated with thehousing of an LIMD.

FIG. 6 illustrates another LIMD.

FIG. 7 illustrates a loop body of an LIMD.

FIG. 8 illustrates another loop body of an LIMD.

FIG. 9 is a simplified view of an LIMD and a patient care system (PCS).

FIG. 10 illustrates a flow chart of calibrating an IMD.

FIG. 11 illustrates a flow chart of a process of recharging an IMD.

FIG. 12 illustrates a system that may be utilized in connection with anIMD, according to an embodiment.

DETAILED DESCRIPTION

FIG. 1 illustrates a leadless intra-cardiac medical device (LIMD) 100implanted within a heart 12 of a patient, according to an embodiment.The heart 12 is generally enclosed in a pericardium, which protects theheart 12, anchors its surrounding structures, and prevents overfillingof the heart 12 with blood. The heart 12 has four chambers, a rightatrium 34, a left atrium 36, a right ventricle 38, and a left ventricle40. In general, the atria 34 and 36 are the receiving chambers, whilethe ventricles 38 and 40 are the discharging chambers. Deoxygenatedblood enters the heart 12 through the superior vena cava 22 or inferiorvena cava 23, for example, and passes into the right atrium 34. Theblood is then pumped through the tricuspid valve 42 into the rightventricle 38 before being pumped out through a pulmonary valve (notshown) into a pulmonary artery 46. The blood is then oxygenated in thelungs and returns to the heart 12 through a pulmonary vein 48 into theleft atrium 36, where it is then pumped through the mitral valve 50 andinto the left ventricle 40. The oxygenated blood then travels from theleft ventricle 40 through the aortic valve (now shown) and into theaorta 54, through which the oxygenated blood is then circulatedthroughout the body.

The LIMD 100 is implanted entirely within the heart 12. The LIMD 100includes a housing 102 configured to be secured to a tissue wall, forexample the wall defining the right ventricle 38 proximate an apex 25 ofthe heart 12. The housing 102 is operatively connected to anintra-cardiac extension 104 that includes a loop body 402 havingmultiple loop segments 421, with the loop segments 421 a and 421 b beingpassively secured within the superior vena cava 22, as explained below.Electrodes 420 are included in the loop segment 421 a on either side andcontact interior wall portions of the superior vena cava 22. In oneembodiment, the intra-cardiac extension 104 is fixedly connected to, andhermitically sealed together with, the electronics housing 102. In thiscase, the intra-cardiac extension 104 cannot be disconnected from theelectronics housing 102 and the LIMD is thus, in essence a singleunitary structure. In other embodiments, the intra-cardiac extension 104may be connected to the electronics housing 102 through a pin/portconnection arrangement, in which case the intra-cardiac extension 104may be disconnected from the electronics housing 102. This configurationmay allow for customization in the form of different sized intra-cardiacextensions for different sized cardiac anatomies.

FIG. 2 illustrates an introducer assembly 200 introducing the LIMD 100into the heart 12, according to an embodiment. The introducer assembly200 includes a flexible tube, such as a catheter, having an internallongitudinal passage 203 into which the LIMD 100, including the loopbody 402 and the housing 102, are retained. The introducer assembly 200is maneuvered by a physician at a proximal end (not shown) into theheart 12 such that the housing 102 is positioned in the right ventricle38 proximate the apex 25. The housing 102 is then anchored in placethrough a securing helix 408.

The introducer assembly 200 is then pulled back in the direction ofarrow A, leaving the housing 102 secured to the heart 12 within theright ventricle 38. The introducer assembly 200 disengages from the LIMD100 as it is pulled away in the direction of arrow A.

FIG. 3 illustrates the introducer assembly 200 disengaging from the LIMD100 within the heart 12, according to an embodiment. As the introducerassembly 200 is pulled back in the direction of arrow A, the anchoredhousing 102 ensures that the LIMD 100 does not retreat along with theintroducer assembly 200. As the introducer assembly 200 slides back inthe direction of arrow A, the flexible loop segments 421, which werepreviously compressed within the introducer assembly 200, are ejectedand expand outwardly. Once the introducer assembly 200 fully disengagesfrom the LIMD 100, the LIMD 100 is implanted entirely within the heart12, as shown in FIG. 1.

FIG. 4A illustrates the LIMD 100 outside of a heart. The LIMD 100includes a housing 102 and an intra-cardiac extension 104 that extendsfrom an end of the module. The intra-cardiac extension 104 has a loopbody 402 connected to a protective tube 404, such as an insulatedsheath, sleeve, or the like. The LIMD 100 may be one of various types ofimplantable devices, such as, for example, an implantable pacemaker, acardiac resynchronization therapy (CRT) device, an implantablecardioverter-defibrillator (“ICD”), neurostimulator, or the like. TheIMD 100 may be configured for DDDR pacing (atrial and ventricularpacing, atrial and ventricular sensing, dual response and rate-adaptive,used for dual chamber pacemakers). In one embodiment, the housing 102includes a cylindrical body 406 having a base 410 and a top end 407. Asecuring helix 408 extends from the base 410 of the body 406 and isconfigured to securely anchor the body 406, and therefore the housing102, to tissue within a chamber of a heart. Instead of a securing helix408, a barb, hook, or the like may extend from the body 406. The tube404 includes insulated conductors that are covered with insulation tomechanically and electrically connect the housing 102 to the loop body402. The tube 404 and loop body 402 may be formed as a single integralstructure. Furthermore, the tube 404 and the loop body 402 may be formedto have substantially uniform stiffness along the entire length.Alternatively, portions of the intra-cardiac extension 104 formed by theloop body 402 and tube 404 may have varying stiffness properties and/orshape memory properties. For example, the tube 404 portion may have noshape memory properties and be less stiff then the loop body 402. Theloop body 402 may have different properties along its length. Forexample, the most distal loop segments 421 a, 421 b may have shapememory properties and greater stiffness than the more proximal loopsegments, which may or may not have shape memory properties.

The housing 102 may include one or more pairs of electrodes forproviding pacing and sensing capabilities. For example, in oneconfiguration, a portion of the helix 408 may be electrically conductiveand function as an electrode. A second electrode 409 may be in the formof a ring around the outer surface of the body 406. The electrodes 408,409 may be configured to deliver lower energy or high energy stimulus,such as pacing pulses, cardioverter pulse trains, defibrillation shocksand the like. The electrodes 408, 409 may also be used to senseelectrical activity, such as physiologic and pathologic behavior andevents.

The loop body 402 of the intra-cardiac extension 104 includes a proximalportion 412, a distal end portion 414, and an intermediate portion 416extending between the proximal portion 412 and the distal end portion414. The loop body 402 includes a series of loop segments 421 that mayhave concentric circular openings 419 through center regions of eachloop segment 421 (for example, similar to a donut). One or more sensingand/or stimulus electrodes 420 may be provided on one or more of theloop segments 421. The electrodes 420 are spaced apart from one anotherby an inter-electrode spacing (for example, the diameter of the loopsegment 421). The electrodes 420 may be wrapped around, or otherwisesecured to, a peripheral portion of a loop segment 421. As shown in FIG.4A, two electrodes 420 are secured around circumferential portions ofthe loop segment 421 a at diametrically opposite sides 422 and 424. Theloop segments 421 are joined to one another at connection links orjoints 426. As shown, the electrodes 420 are distally located from oneanother on the loop segment 421 a and may be positioned generally at aradial angle η that is 90° from a connection link or joint 426 with loopsegment 421 b, for example. The opposed electrodes 420 are configured tocontact tissue portions within a heart, as explained below. The numberof electrodes 420 may vary depending on a particular application. Forexample, additional electrodes may be secured to the loop segment 421 b,or any of the other loop segments 421. Additionally, while theelectrodes 420 are shown at opposite sides 422 and 424 of the loopsegment 421 a, the electrodes 420 may be positioned at various otherlocations on the loop segments 421, and even at different locations fromconnection joints 426. Also, more or less electrodes 420 than thoseshown on the loop segment 421 a may be used. For example, the loopsegment 421 a may include only one electrode 420.

The electrodes 420 may be configured to deliver lower energy or highenergy stimulus, such as pacing pulses, cardioverter pulse trains,defibrillation shocks and the like. The electrodes 420 may also be usedto sense electrical activity, such as physiologic and pathologicbehavior and events.

Each electrode 420 is electrically isolated from the other electrodes420 and from a telemetry conductor 430 contained within the loopsegments 421. Separate terminals and wires (not shown) join theelectrodes 420 and the telemetry conductor 430 to the associatedelectronics in the IMD 100. The telemetry conductor 430 is providedwithin the loop segments 421 of the loop body 402. With reference toFIG. 4B, the telemetry conductor 430 includes windings that are woundinto a series of coil groups 432 to form inductive loops. Each coilgroup 432 may include windings of the insulated conductive wire between1 and 1000 turns, for example. The coil groups 432 operate to receiveand/or transmit radio frequency (RF) energy. The windings in the coilgroups 432 may be formed in a variety of patterns from generallyuniformly shaped circles, ovals and the like. However, the windings orinductive loops of the coil groups 432 are wound in a uniform shape andeach coil group 432, that is connected in series, is wound in a commondirection about a corresponding axis. For example, if one winding iswound in a clock-wise direction about an axis of the associated coilgroup 432, then all of the windings joined in series therewith may bewound in the same clock-wise direction about the same axis or associatedaxes of other coil groups 432. Alternatively, if one winding is wound ina counter-clock-wise direction about an axis of the associated coilgroup 432, then all of the windings joined in series therewith may bewound in the same counter-clock-wise direction about the same axis orassociated axes of other coil groups. As shown, the telemetry conductor430 is not shown in any specific winding pattern. But it is understoodthat the telemetry conductor 430 may be wound in any desired manner toreceive and transmit RF energy that represents communications signals toand from an external programming device.

The telemetry conductor 430 may also be wound with a number of turns andwire gauge sufficient to receive RF energy that represents power that isthen used to charge a battery of the housing 102 joined to the proximalportion 412 of the loop body 402. A telemetry circuit 450 included inthe housing 102 receives signals (e.g., power or data) induced into thetelemetry conductor 430 by RF energy passing about the coil groups 432.The coil groups 432 include at least one partial winding of thetelemetry conductor 430. Optionally, at least one of the coil groups 432may include multiple windings that are at least partially spatiallyoverlapped with one another. The coil groups 432 are distributed alongthe loop body 402 and positioned to be centered along a longitudinalaxis. The telemetry conductor 430 is surrounded by a thin filminsulation (for example, Silicone, OPTIM, polyurethane) to electricallyseparate adjacent windings such that the inductive loops of each coilgroup 432 are insulated from one another (for example, ETFE).

The coil groups 432 may be formed of a single conductive wire, forexample, that connects to the telemetry circuit 450 (discussed below).For example one end of the wire may connect to the telemetry circuit andextend through the tube 404 and extend from the coil groups 432, withthe other end connecting back to the telemetry circuit 450. As such, asingle conductive wire may be contained within all of the loop segments.The single conductive wire forms the coil groups 432 within each loopsegment 421, and extends to another loop segment through a straight linethat passes through the connection joint 426. Optionally, each coilgroup 432 may include a separate and distinct wire coil having first andsecond ends that connect to the telemetry circuit 450.

In accordance with at least one embodiment, one or more of the loopsegments 421 of the loop body 402 are configured to have shape memoryproperties such that they may be squeezable or compressible into asmaller profile that allows them to be loaded into the introducerassembly 200 (shown in FIGS. 2 and 3), such as a cardiac catheter. Forexample, the use of the metal braid or mesh core surrounded by silicon,ETFE, OPTIM and the like may be sufficient to afford the desired amountof shape memory. In the absence of a compressing force, e.g., uponrelease from the introducer assembly, the loop segments assume theirnormally expanded shape having a larger profile. A guiding wire may beattached to the loop body 402 during implantation into a heart. Afterthe loop body 402 is in place, the introducer assembly 200 is extrudedto the last loop segment 421 with a guiding wire holding the last loopsegment 421. Pacing/sensing tests may be performed before the system iscompletely released. If another location attempt is needed, the guidingwire may retract the system.

Optionally, a thermo-responsive shape memory polyurethane (SMPU) may beembedded below and encased within a biocompatible shell (e.g., EFTE).The SMPU represents a smart material that can respond to external heatby changing its macroscopic shape from a temporary configuration to amemorized permanent one. The temporary elongated shape can be maintainedwhile in the sheath which may maintain a certain temperature (thetransition temperature). The sheath may maintain the loop segments 432at this temperature until discharged, after which the material of theloop segments 432 may change temperature. Thereafter, the material inthe loop segments 432 will recover its memorized permanent shape.

The loop segments 421 are located immediately adjacent one another andmay be formed integral with one another. The loop segments 421 may bejoined with one another by linking regions 440, such as the connectionjoints 426. For example, the intermediate portion 416 may be joined tothe distal end portion 414 through a linking region 440. The loopsegments 421, linking regions 440, and distal end portion 414 may beformed integral with one another from a biocompatible electricallyinsulating material, such as silicon, polyurethane, or other materialssuch as copolymers (for example, the Optim® insulation offered by St.Jude Medical, Inc.).

The loop segments 421 have a perimeter 442 that may be flared (forexample, diverges and then re-merges) in a direction generally towardand away from the lateral axis x with respect to the longitudinal axis yof the loop body 402. The loop segments 421 may have different contouredshapes, as shown in FIG. 4A. By way of example, the loop segments 421may have a perimeter, when viewed from the top down, that isdisc-shaped, oval, circular, tubular, rectangular, triangular, and thelike.

The loop segments 421 have opposed top and bottom sides that are alignedgenerally in parallel planes that extend in a generally common directionas the longitudinal axis y. The loop segments 421 are aligned along acommon path. It is recognized that, while FIG. 4A illustrates the loopsegments 421 aligned in a straight manner, this is for illustrationpurposes. When implanted, the loop segments 421 will curve and wrap tofollow the contour of an interior of the heart in a manner determined bythe implanting physician.

FIG. 4B illustrates an isometric view of adjacent loop segments 421 ofthe loop body 402 of the intra-cardiac extension 421. Each loop segment421 includes opposed planar sides 10 and 12 that integrally connect to aperipheral edge 14 and an internal edge 16 that defines the opening 419.

The adjacent loop segments 421 are joined at opposite sides along alongitudinal axis x. Each loop segment 421 includes a coil group 432encased therein. The telemetry conductor 430 may form the coil groups432. Each coil group 432 may include windings arranged in a common planeparallel to the opposed planar sides 10 and 12 as well as the peripheraland internal edges 14 and 16. The coil groups 432 may be formed of asingle conductive wire that forms the telemetry conductor 430, withconnective wire portions 433 within the linking regions 440 thatinterconnect the coil groups 432.

Referring again to FIG. 4A, device electronics (not shown) are providedwithin the housing 102. The electronics and their related functions mayvary depending upon a particular implementation. By way of example, theelectronics may include all of the control logic needed to implement animplantable medical device, such as but not limited to an implantablepacemaker, cardioverter, defibrillator, neurostimulator and the like.The electronics includes one or more rechargeable energy sources such asa rechargeable battery. The electronics may also include a chargestorage device depending upon the functionality to be performed. Forexample, if the IMD 100 delivers stimulus pulses, the charge storagedevice may include one or more capacitors that are sufficient incapacity to deliver the desired stimulus. Alternatively, the electronicsmay have a more limited subset of components configured to implementonly a portion of the functionality available in an implantable medicaldevice.

FIG. 5 illustrates a block diagram of a housing 102 portion of an LIMD100, which may be capable of treating one or both of fast and slowarrhythmias with stimulation therapy, including cardioversion,defibrillation, and pacing stimulation, according to an embodiment.While a particular multi-chamber device is shown, this is forillustration purposes only. It is understood that the appropriatecircuitry could be duplicated, eliminated or disabled in any desiredcombination to provide a device capable of simply monitoring impedanceand/or cardiac signals, and/or treating the appropriate chamber(s) withcardioversion, defibrillation and pacing stimulation.

By way of example only, the housing 102 may form part of a “nano”pacemaker that may be packaged in a very compact and small manner havinga form factor substantially similar to the form factor of the loop body402. The body 406 of the device housing 102 may have a cross-sectionthat is no larger than the cross-section of the loop body 402.Alternatively, the housing may have a disc shape when viewed from thetop down and have a small thickness or height, where the disc shape andthe thickness/height are substantially the same as the disc shape andthickness of the loop body.

The body 406 of the housing 102 is often referred to as the “can”,“case” or “case electrode” and may be programmably selected to act asthe return electrode for some or all sensing modes. The body 406 mayfurther be used as a return electrode alone or in combination with oneor more of the other electrodes. The electronics within the housing 102include a plurality of terminals 502, 504, 506, 508. To achieve sensing,pacing and shocking in desired chambers of the heart, the terminals areselectively connected to corresponding combinations of electrodes,including electrodes 408, 409 on the housing 102 and electrodes 420 onthe intra-cardiac extension 104.

The housing 102 includes a programmable microcontroller 510 thatcontrols the various modes of sensing and stimulation therapy. Themicrocontroller 510 includes a microprocessor, or equivalent controlcircuitry, designed specifically for controlling the delivery ofstimulation therapy and may further include RAM or ROM memory, logic andtiming circuitry, state machine circuitry, and I/O circuitry. Themicrocontroller 510 includes the ability to process or monitor inputsignals (data) as controlled by a program code stored in memory. Thedetails of the design and operation of the microcontroller 510 are notcritical. Rather, any suitable microcontroller 510 may be used. Themicrocontroller 510 may analyze sensed signals and determine when anarrhythmia (e.g., fibrillation) is occurring. The microcontroller 510may detect arrhythmias, such as ventricular tachycardia (VT),bradycardia and ventricular fibrillation (VF). The microcontroller 510may perform morphology detection to analyze the morphology of thecardiac signal, including detecting R wave peaks and/or detecting T wavefeatures of interest, such as onset, peak, etc.

The housing 102 includes a rechargeable or non-rechargeable battery 536and one or more energy storage units 512, 514, 528, such as a pluralityof capacitors. The energy storage units may vary depending upon thefunctionality desired to be supplied by the housing 102. For example,when the housing 102 affords all of the functionality of adefibrillator, the storage unit represents a shocking circuit 528 havinghigh voltage capacitors capable of storing large amounts of energyneeded to deliver defibrillation shocks. When the housing 102electronics functions as a pacemaker, the storage unit may represent anatrial pulse generator 512 and/or a ventricular pulse generator 514having capacitors capable of storing the amount of energy needed todelivery low voltage pacing pulses.

Control logic is provided on an integrated circuit (IC). The controllogic includes various electronic components based on the desiredfunctionality of the housing 102. By way of example, the control logicincludes the processor 510, a switching bridge 516, andanalog-to-digital (A/D) converters 524. The switching bridge 516interfaces with multiple input terminals 502, 504, 506, 508 that areconfigured to be coupled to terminals connected to the atrial electrodes420 and the ventricular electrodes 408, 409 through wires within theintra-cardiac extension 104. Optionally, more inputs may be includesbased on the number of electrodes and telemetry coils.

The housing 102 includes the telemetry circuit 450 that is configured toreceive signals that are detected by the telemetry conductor 430, aswell as transmit signals to the telemetry conductor 430 that are thenwirelessly transmitted as RF energy to an external device 526. Thetelemetry circuit 450 includes a transceiver that performs modulationupon outgoing data signals and performs demodulation upon incoming datasignals. For example, the telemetry conductor 430 may receive, in the RFenergy, data signals such as commands, parameters, thresholds and thelike. As one optional exemplary implementation for incoming data, thetelemetry circuit 450 may detect analog data signals sensed by the coilgroups 432, convert the analog data signals into digital data packetsand convey the data packets to the processor 510. As one optionalexemplary implementation for outgoing data, the telemetry circuit 450receives data packets from the processor 510, converts the data packetsto analog data signals and transmits the analog data signals over thecoil groups 432. Optionally, for outgoing data transmissions, thetelemetry circuit 450 may packetize data segments in accordance with apredetermined wireless transmission protocol, such as by dividing anoutgoing data stream into segments, and packetize each data segment withheader and footer information. Similarly, incoming data transmissionsmay be formatted in accordance with a predetermined transmissionsprotocol. The telemetry circuit 450 may temporally buffer incoming datatransmissions, parse the stored inbound data stream for header and/orfooter information, and extract the data content from the inbound datastream. The telemetry circuit 450 may then convey data content to theprocessor 510 with or without reformatting and/or repackaging the datacontent.

With respect to the rechargeable battery 536, the telemetry conductor430 may receive, through RF energy, a power signal that is used torecharge the battery 536. A power conversion unit (not shown) convertsRF energy received on telemetry conductor 430 into a power supply signalthat can recharge the battery 536 (for example, to a desired voltagerange and/or current level). As explained below, the RF energy generatesa magnetic field, which, in turn, induces a current within the loopsegments that is used to recharge the battery 536. Optionally, thetelemetry conductor 430 may receive power in the RF signal that isrouted directly to an energy storage unit 512, 514, 528 to directlycharge capacitors before the capacitors deliver a low or high energystimulus (for example, pace or defibrillation.)

The atrial pulse generator 512 and a ventricular pulse generator 514generate pacing and ATP stimulation pulses for delivery by desiredelectrodes. The electrode configuration switch 516 (also referred to asswitch bank) controls which terminals 502, 504, 506, 508 receiveelectrical signals, shocks or pacing pulses. The pulse generators 512,514 are controlled by the microcontroller 510 via appropriate controlsignals respectively, to trigger or inhibit stimulation pulses. Themicrocontroller 510 controls the timing of such stimulation pulses(e.g., pacing rate, atrio-ventricular (AV) delay, atrial interconduction(A-A) delay, or ventricular interconduction (V-V) delay, etc.) as wellas to keep track of the timing of refractory periods, PVARP intervals,noise detection windows, evoked response windows, alert intervals,marker channel timing, etc.

A ventricular sensing circuit 518 may amplify, filter, digitize and/orotherwise process cardiac signals sensed using the electrodes. Thecircuit 518 may provide separate, combined or difference signals to themicrocontroller 510 representative of the sensed signals from the RVelectrodes 408, 409. An atrial sensing circuit 520 is connected throughthe switch 516 to RA electrodes 420 to sense RA cardiac activity. Theswitch 516 also connects various combinations of the electrodes to animpedance measurement circuit 522.

The impedance measuring circuit 522 collects impedance measurementsbetween corresponding combinations of electrodes. For example, theimpedance measuring circuit 522 may collect measured impedance for eachor a subset of the sensing vectors. The impedance measurements are takenalong one or more vectors through the heart over a period of time. Theimpedance measurements are supplied to the controller 510.

The switch 516 determines the “sensing polarity” of the cardiac signalby selectively closing the appropriate switches. The outputs of theatrial and ventricular sensing circuits 518, 520 are connected to themicrocontroller 510 which, in turn, is able to trigger or inhibit theatrial and ventricular pulse generators 512, 514, respectively. Thesensing circuits 518, 520, in turn, receive control signals over signallines from the microcontroller 510 for purposes of controlling the gain,threshold, the polarization charge removal circuitry (not shown), andthe timing of any blocking circuitry (not shown) coupled to the inputsof the sensing circuits 518, 520.

Cardiac signals are also applied to the inputs of an analog-to-digital(ND) data acquisition system 524. The data acquisition system 524 isconfigured to acquire intracardiac electrogram signals, convert the rawanalog data into a digital signal, and store the digital signals forlater processing and/or telemetric transmission to an external device526. The data acquisition system 524 samples cardiac signals across anypair of desired electrodes. The microcontroller 510 further controls theshocking circuit 528 by way of a control signal. The shocking circuit528 generates stimulating pulses of low (up to 0.5 Joules), moderate(0.5-10 Joules), or high energy (11 to 40 Joules), as controlled by themicrocontroller 510. Stimulating pulses are applied to the patient'sheart through at least two shocking electrodes.

The microcontroller 510 is further coupled to a memory 530 by a suitabledata/address bus. The memory 530 stores programmable operating,impedance measurements, impedance derivation and therapy-relatedparameters used by the microcontroller 510. The operating andtherapy-related parameters define, for example, surrogate signals,contractility estimates, models, length force curves, correctionfactors, trend values, pacing pulse amplitude, pulse duration, electrodepolarity, rate, sensitivity, automatic features, arrhythmia detectioncriteria, and the amplitude, wave shape and vector of each stimulatingpulse to be delivered to the patient's heart within each respective tierof therapy.

The operating and therapy-related parameters may be non-invasivelyprogrammed into the memory 530 through the telemetry circuit 450 intelemetric communication with the external device 526, such as aprogrammer, trans-telephonic transceiver, or a diagnostic systemanalyzer. The telemetry circuit 450 is activated by the microcontroller510. The telemetry circuit 450 advantageously allows intracardiacelectrograms, cardiogenic impedance (CI) measurements, surrogatesignals, contractility estimates, correction factors, models, trendvalues and status information relating to the operation of the LIMD 100to be sent to and from the external device 526 through an establishedcommunication link 532.

The housing 102 may include one or more surrogate sensors 534. Thesurrogate sensor(s) 534 produces surrogate signals representative ofestimates for at least one of cardiac volume and pressure of the heartwhen the impedance measurements were taken. For example, the surrogatesensor 534 may sense estimates of end diastolic volume, blood pressure,heart rate, stroke volume, patient activity, respiration rate and thelike. Optionally, the surrogate sensor 534 may produce surrogate signalsby identifying features of interest form the impedance measurements. Forexample, the sensor 534 may collect and filter impedance signals alongone or more impedance sensing vectors. The sensor 534 may include alow-pass, band pass and/or high pass filter to filter the impedancemeasurements and produce non-contractility information.

The sensors 534 may include one or more of an accelerometer, a pressuresensor, a heart sound sensor, a pulse oximetry sensor, a flow sensor andthe like. While a sensor 534 is shown within the housing, optionally,one or more sensors may be located outside the housing and coupledthereto through a connector. The sensor 534 may detect a level of orchanges in cardiac output, a level of changes in the physiologicalcondition of the heart, or a level of or changes in activity (e.g.,detecting sleep and wake states). The battery 536, such as therechargeable battery discussed above, provides operating power to all ofthe circuits shown.

The controller 510 includes, among other things, various modules toperform select types of analysis. For example, an arrhythmia detectionmodule 538 may analyze sensed signals and identifies various types ofarrhythmias. An ST segment analysis module 540 may analyze variouscharacteristics of ST segments over multiple cardiac cycles to identifychanges or patterns that are indicative of certain conditions ofinterest. An ischemia detection module 542 may analyze sensed signals toidentify different types of ischemia. An impedance analysis module 544may analyze impedance measurements and, based thereon, derive estimatesof cardiac output and the like.

When the LIMD 100 is located deep within the heart, as compared withsubcutaneous implants, the signals transmitted to/from the coil groups432 may be weaker. Optionally, more or fewer coil windings may beincluded within each coil group 432 depending upon whether theintra-cardiac extension 104 is intended to be implanted shallower ordeeper. Embodiments described herein may utilize waved multi-loop coilgroups 432. Each coil group 432 represents an inductor. By joining thecoil groups 432 electrically in series, a series of inductors are formedto achieve coupling and signal linkage through telemetry with desiredimplanted or external components.

By way of example, the insulated wires of the electrodes 420 and thetelemetry conductor 430 may be made of biocompatible metals (DFT orCopper, or the like). The coating of the wires may be ETFE and the wiresmay be embedded inside Silicone or another material.

FIG. 6 illustrates an LIMD 600 according to another embodiment. The LIMD600 is similar to the LIMD 100 illustrated in FIG. 4, except that thisembodiment of the LIMD 600 includes an intra-cardiac extension 604 witha loop body 602 that is formed as a solid body without openings throughloop segments 606. Additionally, electrodes 608 are secured to an outerportion of at least one of the loop segments 606. Because the loopsegments 606 are contiguous, solid discs, as opposed to donut-shapedrings, a telemetry conductor 610 contained within each loop segment 606may be contained within a greater area. As such, each loop segment 606may include more windings.

Referring to FIGS. 4-6, the telemetry conductor 430, 610 may receive RFenergy from an external programmer/handheld wireless control devices.The RF energy may represent wireless communications and/or power torecharge the battery 536. The handheld device may be a traditionalprogrammer or may be a small portable device such as an iPOD-likedevice. The external device serves as a control unit that can upload andstore data daily as well as program pacing/sensing parameters, pacingmodes and device check-ups. The handheld device also providestransferring data to remote systems or patient home care systems. Thehandheld device may have a display screen for viewing signals andresults. The programmer may be used to check battery life and torecharge the battery 536 by conveying battery power over the RF signal.

Referring to FIGS. 1-6, the LIMD 100, 600 may be contained within theintroducer assembly 200, such as a flexible catheter. A physician orsurgeon operates the introducer assembly at a proximal end (not shown).The proximal end may include controls that allow the introducer assemblyto be bent, curved, canted, rotated, twisted, or the like, so as to benavigated through a patient's vasculature.

In order to implant the LIMD 100, 600 into the heart 12, the introducerassembly 200 containing the LIMD 100, 600 is introduced into a vein of apatient. During this time, a separate and distinct imaging system, suchas a fluoroscopic imaging system, and/or a surgical navigation systemmay be used to assist in guiding the LIMD 100, 600 into the heart 12.For example, a surgeon may view a real-time fluoroscopic image of thepatient's anatomy to see the compressed LIMD 100, 600 within theintroducer assembly being maneuvered through patient anatomy.

The introducer assembly 200 is maneuvered through the vein andultimately into the superior vena cava 22, for example, and into theright atrium 34. Optionally, the introducer assembly 200 may bemaneuvered from a vein that connects to the inferior vena cava 23 andinto the right atrium 34. Also alternatively, the introducer assembly200 containing the LIMD 100, 600 may be introduced into other chambersof the heart through arteries, for example. In general, the LIMD 100,600 may be introduced into a chamber of a heart through the introducerassembly 200.

Once in the heart 12, the housing 102 is implanted into tissue of theheart wall 12, such as proximate the apex 25 within the right ventricle38. The securing helix 408 may securely fasten the housing 102 to thetissue of the heart wall. The protective tube 404 passes out of theright ventricle 38 and through the tricuspid valve 42. As the tubularcatheter of the introducer assembly 200 slides out of engagement withthe loop body 402, the compressed loop segments 421 eject from theintroducer assembly 200 and assume their normally expand state withinthe heart 12. As shown, the loop segment 421 a expands within thesuperior vena cava 22 such that the electrodes 420 contact interior wallportions of the superior vena cava 22. Additionally, other loop segments421 may include electrodes that contact interior wall portions of theheart.

As shown in FIG. 1, the loop segments 421 a and 421 b may be configuredto have diameters that may be larger than the inner diameter of thesuperior vena cava 22. In this manner, the loop segments 421 a and 421 bmay be passively fixed to the superior vena cava 22, with the rest ofthe IMD 100 retained within the heart 12. In particular, the remainingloop segments 421 are within the right atrium 34, the protective sheath404 passes through the tricuspid valve 42, and the body 406 housing 102is secured to tissue of the right ventricle 38. The diameter of the loopsegment 421 b also ensures that the electrodes 420, which may be sensingand/or stimulus electrodes, abut against interior walls that define thesuperior vena cava 22.

Other loop segments 421 may be sized and shaped to make contact withwall portions that define the right atrium 34, for example, so thatadditional sensing and/or pacing electrodes abut against wall portionsof the right atrium 34. Moreover, the LIMD 100 may be positioned withinother chambers of the heart 12.

Thus, as shown, the LIMD 100, 600 is completely within the heart 12. Noportion of the LIMD 100, 600 passes out of the heart. The loop body 402is configured to be used in conjunction with a telemetry system torecharge the battery 536. Accordingly, a smaller battery may be usedwithin the LIMD 100, 600 because it may be periodically re-charged. Thisis in contrast to a non-chargeable battery that typically needs to belarge enough to provide sufficient power over a long period of time.Therefore, the form factor and overall size of the housing 102 may becompact.

FIG. 7 illustrates a loop body 402 a, according to an embodiment. Inthis figure (and FIG. 8), the loop segments 421 are in the form of discsinstead of rings (as shown in FIG. 4A) in order to more clearlyillustrated the wound arrangement of coil groups 432. As shown in FIG.7, the loop body 402 a includes a plurality of loop segments 421. Theloop segments 421 are generally aligned with one another about thelongitudinal axis y. Each loop segment 421 may be coplanar with oneanother (as shown in FIG. 7). That is, if laid flat on a planar surface,all of the loop segment 421 s would be contained within the sameplane(s). In general, the loop segments 421 are oriented the same withrespect to orthogonal axes x, y, and z. More or less loop segments 421may be used. Further, one or more of the loop segments 421 may includesensing and/or stimulus electrodes, such as the electrodes 420 shown inFIG. 4A. Further, each loop segment 421 may be a donut-shaped segmenthaving a central passage, such as shown and described with respect toFIGS. 4 a and 4 b, or a solid disc, such as shown and described withrespect to FIG. 6.

FIG. 8 illustrates a loop body 402 b, according to an embodiment. Asshown in FIG. 8, the loop body 402 b includes a plurality of first loopsegments 421′ connected to adjacent second loop segments 421″. The firstloop segments 421′ are generally aligned and oriented in common with oneanother, while the second loop segments 421″ are generally aligned andoriented in common with one another. However, each first loop segment421′ may be generally 90° out of plane with each second loop segment421″ with respect to the orthogonal axes x, y, and z. For example, whilethe first loop segments 421′ are oriented along the x and y axes, thesecond loop segments 421″ are oriented along the y and z axes. More orless first and second loop segments 421′, 421″ may be used. Further, oneor more of the first or second loop segments 421′, 421″ may includesensing and/or stimulus electrodes. Further, each loop segment 421′,421″ may be a donut-shaped segment having a central passage, such asshown and described with respect to FIGS. 4 a and 4 b, or a solid disc,such as shown and described with respect to FIG. 6. Optionally, the loopsegments 421′, 421″ may be out of plane at other angles besides 90°. Forexample, the loop segments 421′, 421″ may be out of plane by 360°/numberof loops. For example, if the loop body 402 b includes three loopsegments, each segment may be 120° out of plane with respect to aneighboring loop segment.

The loop segments may be oriented with respect to other planes. Forexample, one loop segment may be out plane with another loop segment,which may be out of plane with respect to another loop segment. The loopsegments may be oriented with respect to different planes in relation toone another so that they may be oriented with respect to differentmagnetic fields (generated by RF energy) passing through the loop body402 b. A magnetic field induces a current in the conductive wire of theloop. Orienting the loop segments at varying angles allows the loopsegments to provide recharging power to the battery and communicate withthe telemetry circuit 450. Thus, if current from a magnetic field is notinduced through a first loop segment due to its orientation with respectto the planes x, y, and z, current will be induced through a secondand/or third loop segment that are oriented differently from the firstloop segment.

A changing magnetic flux induces an electromotive force (emf) and acurrent in the coil groups 432 of the loop segments 421. A changingmagnetic flux produces an electric field in the coil groups 432. Varyingthe orientations of the loop segments allows them to harness currentinduced by changing magnetic fields, and therefore pass that inducedcurrent to the rechargeable battery 536 of the housing 102.

FIG. 9 is a simplified view of a patient care network 900. In oneconfiguration, the network includes the LIMD 100, a patient care system(PCS) 902, and a server 904. The PCS 902 corresponds to the externaldevice 526 in FIG. 5. As discussed above, the IMD 100 is locatedentirely within the heart 12 of a patient. The remotely-located PCS 902monitors and communicated with the LIMD 100 through RF telemetry. ThePCS 902 may be located within a home, vehicle, office, and the like.When, the PCS 902 is located within the patient's home, it may beproximate the patient's bed. The PCS 902 functions as a base stationthat wirelessly communicates with the LIMD 100. The PCS 902 alsocommunications with the remote server 904 within the patient carenetwork 900, such as over a phone link, cellular link, Internetconnection, local area network, wide area network and the like.

The PCS 902 performs various functions, such as operating as anintermediate relay device to collect and store patient physiologic data,LIMD operational status data and the like. The PCS 902 then transmitsthe physiologic data, LIMD operational status data and other data to theremote server 904 of the patient care network. Physicians and otherpersonnel can monitor the patient and collect data over the patient carenetwork. Also, the PCS 902 may receive updates, upgrades and other LIMDcontrol-related information from the patient care network and relay theLIMD control-related information to the LIMD 100.

When the LIMD 100 is in the presence of a magnetic field, such as causedby RF energy when a wand 906, 908 is proximate the LIMD 100, currentflow is induced in the coil groups 432 within the loop segments 421. Theinduced current passes to the rechargeable battery 536 of the body 406of the housing 102. In this manner, the battery 536 is recharged.

FIG. 10 illustrates a flow chart of calibrating the LIMD 100, accordingto an embodiment of the present invention. Referring to FIGS. 1-5, 9,and 10, for example, the LIMD 100 may be calibrated after the LIMD 100is implanted into the heart 12 of the patient. In general, thecalibration process begins when an external device 526 (FIG. 5) (e.g.PCS 902 or programmer) instructs the LIMD 100 to enter a calibrationmode. The external device 526 then begins to transmit a predetermined RFsignal to the LIMD 100. The LIMD 100 may provide feedback to theexternal device 526 from the LIMD 100. The external device 526 mayinstruct a physician, technician or a patient how to optimize chargingand communication properties of the LIMD 100 and external device 526.

Each patient exhibits a different anatomical shape and thus the loopsegments 421 may experience different amounts/degrees of couple to theexternal wand of the external device 526 based on the patient. Tocompensate for these differences in individuals, the resonantfrequencies of the coil groups 432 within the loop segments 421 may betuned and adjusted by adjusting one or both of the capacitance andinductance within the RF antenna system created by the coil groups 432and the electronics of the IMD 100. For example, the telemetry circuit450 may have a variable inductor or capacitor therein that can beadjusted to change the resonant frequency of the loop segments 421.

As the loop segments 421 move within the heart 12 (due to patientmovement, contractions of the heart, and the like), the shapes of thecoil groups 432 change, thereby also potentially causing inductance andcapacitance to change. The physician or patient may monitor thesechanges through the external device 526. Therefore, at 1000, a physicianmonitors changes in inductance and capacitance of the loop segments 421within the heart 12.

At 1002, the display of the external device 526 may then displayinstructions for adjusting drive frequencies of the IMD 100 and/orpositions of the wands 906, 908 in relation to the IMD 100. A change indrive frequency, such as 50 Hz±5 Hz, and/or the presence of the RF fieldgenerated by the wands 906, 908, may be used to compensate for thechanging inductance and capacitance within the coil groups 432.

At 1004, the physician or technician may tune the loop segments 421 byadjusting the drive frequencies based on instructions shown on thedisplay of the external device 526. The external device 526 may instructthe physician or patient how best to optimize the driving frequency ofthe LIMD 100 in order to optimize battery recharging, and communicationbetween the LIMD 100 and the external device 526. Optionally, thephysician may use the external device 526 to program the LIMD 100 withnew values for resonant frequency parameters. Optionally, the LIMD 100may automatically adjust its capacitance and/or inductance to achieveautomated self tuning.

FIG. 11 illustrates a flow chart of a process of recharging an LIMD,according to an embodiment. At 1100, a communication session isinitiated between a patient care system (PCS) and the LIMD. Next, at1102, the LIMD transmits battery status to the PCS. The PCS thendetermines the battery status at 1104. If, at 1106, the charging levelof the battery within the LIMD is above a low battery threshold, theprocess returns to 1104. If, however, the charging level of the batteryis at or below the low battery threshold, the PCS activates the LIMDinto a recharge mode at 1108. In the recharge mode, an RF signal isgenerated proximate the loop segments of the LIMD at 1110. That is, theloop segments are in the presence of RF energy. The RF energy generatesa magnetic field at 1112. The magnetic field induces current flow withinthe LIMD that passes from the loop segments to the rechargeable batterywithin the housing at 1114. The current then charges the battery at1116. The process then returns to 1102.

Referring again to FIGS. 1-5, for example, as noted, an excitation RFsignal induces current flow in the coil groups 432 within the loopsegments 421. The current flows from the loop segments 421 to the body406 of the housing 102 as an AC signal, thereby generating a voltage ofbetween 1-10 V, for example, at the body 406 of the housing 102. If thevoltage is too low to recharge the battery 536, the voltage may bestepped up to a suitable voltage, such as 3-6 V, for example. If thevoltage is sufficient for charging, there is no need to step up thevoltage. The AC current may then pass through a rectifier having diodesthat rectify the signal to DC. The DC signal may then be filtered andpassed to a voltage regulating circuit that monitors battery voltage,current, and temperature of the battery 536 to protect againstover-charging or damaging the battery. For example, if the battery 536is heating up too fast, the charging process may be slowed or haltedaltogether. The electronics describe above may be included in thetelemetry circuit 450 of the housing 102.

FIG. 12 illustrates a system network 1200 that may be utilized inconnection with the LIMD 100 (FIG. 4) or 600 (FIG. 6), according to anembodiment. The system network 1200 may include a server 1202 connectedto a database 1204, a programmer 1206, a local RF transceiver 1208 and auser workstation 1210 electrically connected to a communication system1212. The communication system 1212 may be the internet, a voice over IP(VoIP) gateway, a local plain old telephone service (POTS) such as apublic switched telephone network (PSTN), a cellular phone basednetwork, and the like. Alternatively, the communication system 1212 maybe a local area network (LAN), a campus area network (CAN), ametropolitan area network (MAN), or a wide area network (WAM). Thecommunication system 1212 serves to provide a network that facilitatesthe transfer/receipt of information.

The system 1200 includes the LIMD 100, for example, implemented inaccordance with embodiments discussed. The LIMD 100 may be locatedwithin a heart of a patient, as discussed above.

The server 1202 is a computer system that provides services to othercomputing systems over a computer network. The server 1202 interfaceswith the communication system 1212 to transfer information between theprogrammer 1206, the local RF transceiver 1208, the user workstation1210 as well as a cell phone 1214, and a personal data assistant (PDA)1216 to the database 1204 for storage/retrieval of records ofinformation. On the other hand, the server 1202 may upload raw cardiacsignals from a surface ECG unit 1220 or the LIMD 100 via the local RFtransceiver 1208 or the programmer 1206.

The database 1204 stores information such as the measurements for theelectrical cardiac signals, the electrophysiologic response parameters,and the like, for a single or multiple patients. The information isdownloaded into the database 1204 via the server 1202 or, alternatively,the information is uploaded to the server from the database 1204. Theprogrammer 1206 may reside in a patient's home, a hospital, or aphysician's office. Programmer 1206 interfaces with the surface ECG unit1220 and the LIMD 100. The programmer 1206 may wirelessly communicatewith the LIMD 100 and utilize protocols, such as Bluetooth, GSM,infrared wireless LANs, HIPERLAN, 3G, satellite, as well as circuit andpacket data protocols, and the like. The programmer 1206 is able toacquire cardiac signals from the surface of a person (e.g., ECGs),intra-cardiac electrogram (e.g., IEGM) signals from the LIMD 100, and/orvalues of cardiogenic impedance parameters and electrophysiologicresponse parameters from the LIMD 100. The programmer 1206 interfaceswith the communication system 1212, either via the internet or via POTS,to upload the information acquired from the surface ECG unit 1220 or theLIMD 100 to the server 1202.

The local RF transceiver 1208 interfaces with the communication system1212, via a communication link 1224, to upload data acquired from thesurface ECG unit 1220 and/or from LIMD 100 to the server 1202. In oneembodiment, the surface ECG unit 1220 and the LIMD 100 have abi-directional connection with the local RF transceiver via a wirelessconnection. The local RF transceiver 1208 is able to acquire cardiacsignals from the LIMD 100. On the other hand, the local RF transceiver1208 may download stored data, parameters, cardiac data, and the like,from the database 1204 to the LIMD 100.

The user workstation 1210 may interface with the communication system1212 via the internet or POTS to download values of the cardiogenicimpedance parameters and electrophysiologic response parameters via theserver 1202 from the database 1204. Alternatively, the user workstation1210 may download raw data from the surface ECG unit 1220 or LIMD 100via either the programmer 1206 or the local RF transceiver 1208. Theuser workstation 1210 may download the information and notifications tothe cell phone 1214, the PDA 1216, the local RF transceiver 1208, theprogrammer 1206, or to the server 1202 to be stored on the database1204. For example, the user workstation 1210 may communicate anidentified potential cause of pulmonary edema to the cell phone 1214 ofa patient or physician.

As explained above, embodiments provide an implantable medical device(IMD) that is compact and configured to be retained within chambers of aheart. Moreover, because the battery of the IMD is rechargeable, asmaller, less bulky battery may be used, as compared to known systems.Therefore, a housing of the IMD may be smaller and occupy a relativelysmall volume within the heart.

Embodiments herein utilize an intra-cardiac extension having a distalextension portion that is pre-formed into planar disc-shaped segments. Aproximal end of the IC extension is coupled to a housing. The proximalend of the IC extension is configured to be located in a local chamberof the heart, while the distal extension portion is configured to extendinto an adjacent chamber of the heart. For example, the housing andproximal end of the IC extension may be located in the right ventricleor left ventricle, while the distal extension portion of the ICextension extends through the tricuspid or mitral valve, respectively,into the corresponding one of the right atrium or left atrium.

It is to be understood that the above description is intended to beillustrative, and not restrictive. For example, the above-describedembodiments (and/or aspects thereof) may be used in combination witheach other. In addition, many modifications may be made to adapt aparticular situation or material to the teachings of the inventionwithout departing from its scope. While the dimensions, types ofmaterials and coatings described herein are intended to define theparameters of the invention, they are by no means limiting and areexemplary embodiments. Many other embodiments will be apparent to thoseof skill in the art upon reviewing the above description. The scope ofthe invention should, therefore, be determined with reference to theappended claims, along with the full scope of equivalents to which suchclaims are entitled. In the appended claims, the terms “including” and“in which” are used as the plain-English equivalents of the respectiveterms “comprising” and “wherein.” Moreover, in the following claims, theterms “first,” “second,” and “third,” etc. are used merely as labels,and are not intended to impose numerical requirements on their objects.Further, the limitations of the following claims are not written inmeans-plus-function format and are not intended to be interpreted basedon 35 U.S.C. §112, sixth paragraph, unless and until such claimlimitations expressly use the phrase “means for” followed by a statementof function void of further structure.

What is claimed is:
 1. A leadless intra-cardiac medical device (LIMD)configured to be implanted entirely within a heart of a patient, theLIMD comprising: an intra-cardiac extension comprising a loop body, theloop body comprising at least one loop segment, the loop segmentcomprising at least one coil group that is configured to one or both ofreceive and transmit radio frequency (RF) energy, wherein the loop bodyis configured to extend into a first chamber of the heart; and a housingin electrical communication within the loop body, the housing comprisinga transceiver, wherein the housing is configured to be securely attachedto an interior wall portion of a second chamber of the heart, whereinthe transceiver is configured to communicate with an external devicethrough the RF energy, wherein the at least one loop segment is distallylocated from the housing and further comprises a contiguous, solid discand at least one electrode, wherein the electrode is secured to an outerportion of the loop segment.
 2. The device of claim 1, wherein thehousing further comprises an energy source configured to be rechargedthrough current induced within the at least one coil group, and whereinthe current is induced by a magnetic field caused by the RF energy. 3.The device of claim 1, wherein the at least one loop segment isconfigured to contact a portion of an internal wall of the heart, andwherein the housing further comprises electronics configured to provideone or both of sensing or stimulus through the at least one electrode.4. The device of claim 1, wherein the at least one loop segment includesa plurality of interconnected loop segments.
 5. The device of claim 4,wherein each of the plurality of interconnected loop segments arecommonly aligned and oriented with respect to one another.
 6. The deviceof claim 4, wherein the plurality of interconnected loop segmentsincludes a first group of loop segments and a second group of loopsegments, wherein the first group of loop segments is oriented withrespect to first and second orthogonal axes and the second group of loopsegments is oriented with respect to first and third orthogonal axes. 7.The device of claim 4, wherein a first of the plurality ofinterconnected loop segments is aligned in a first orientation and asecond of the plurality of interconnected loop segments is aligned in asecond orientation, and wherein the first orientation differs from thesecond orientation so that the first and second of the plurality ofinterconnected loop segments are out of plane with one another.
 8. Thedevice of claim 1, wherein the at least one loop segment comprises aperimeter that flares in a direction generally toward and away from alateral axis with respect to a longitudinal axis of the loop body. 9.The device of claim 1, further comprising a protective tube between theloop body and the housing.
 10. A leadless intra-cardiac medical device(LIMD) configured to be implanted entirely within a heart of a patient,the device comprising: a housing configured to be securely attached toan interior wall portion of a first chamber of the heart, the housinghaving a proximal end and a distal end, and the housing hermeticallyenclosing a telemetry circuit, the telemetry circuit comprising atransceiver, wherein the transceiver is configured to communicate withan external device through radio frequency (RF) energy; and anintracardiac (IC) extension extending from the distal end of thehousing, the IC extension having a proximal end directly connected tothe distal end of the housing, the IC extension having a distal endcomprising a loop body configured to extend into a second chamber of theheart, the loop body comprising at least one loop segment, the loopsegment comprising at least one coil group, the coil group configured toone or both of receive and transmit the RF energy, wherein the loopsegment has a resonant frequency, and wherein the telemetry circuit isconfigured to adjust the resonant frequency of the loop segment.
 11. Theleadless intra-cardiac medical device of claim 10, wherein the housingfurther comprising a battery, and wherein the coil group of the loopsegment is configured to induce current flow and pass the current flowto the battery when the LIMD is in the presence of a magnetic field. 12.A leadless intra-cardiac medical device (LIMD) configured to beimplanted entirely within a heart of a patient, the LIMD comprising: anintra-cardiac extension comprising a loop body, the loop body comprisingat least one loop segment, the loop segment comprising at least one coilgroup that is configured to one or both of receive and transmit radiofrequency (RF) energy, wherein the loop body is configured to extendinto a first chamber of the heart, wherein the at least one loop segmentincludes a plurality of interconnected loop segments, wherein theplurality of interconnected loop segments includes a first group of loopsegments and a second group of loop segments, wherein the first group ofloop segments is oriented with respect to first and second orthogonalaxes and the second group of loop segments is oriented with respect tofirst and third orthogonal axes; and a housing in electricalcommunication within the loop body, the housing comprising atransceiver, wherein the housing is configured to be securely attachedto an interior wall portion of a second chamber of the heart, whereinthe transceiver is configured to communicate with an external devicethrough the RF energy.
 13. The device of claim 12, wherein the at leastone loop segment comprises a perimeter shaped as a disc, oval, circle,tube, rectangle, or triangle.